Proppant particulates formed from flexicoke and methods related thereto

ABSTRACT

Proppant particulates like sand are commonly used in hydraulic fracturing operations to maintain one or more fractures in an opened state following the release of hydraulic pressure. Fracturing fluids and methods of hydraulic fracturing may also use proppant particulates composed of flexicoke material. Such proppant particulates may have improved transport into fractures because of lower density than traditional proppants like sand and may produce fewer fines that reduce fluid flow through proppant packs.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalApplication No. 62/971,529 filed Feb. 7, 2020, the entire contents ofwhich are herein incorporated by reference in their entireties.

FIELD OF THE INVENTION

The present disclosure relates to fracturing operations and proppantparticulates employed therein.

BACKGROUND OF THE INVENTION

A wellbore may be drilled into a subterranean formation in order topromote removal (production) of a hydrocarbon or water resourcetherefrom. In many cases, the subterranean formation needs to bestimulated in some manner in order to promote removal of the resource.Stimulation operations may include any operation performed upon thematrix of a subterranean formation in order to improve fluidconductivity there through, including hydraulic fracturing, which is acommon stimulation operation for unconventional reservoirs.

Hydraulic fracturing operations pump large quantities of fluid into asubterranean formation (e.g., a low-permeability formation) under highhydraulic pressure to promote formation of one or more fractures withinthe matrix of the subterranean formation and create high-conductivityflow paths. Primary fractures extending from the wellbore and, in someinstances, secondary fractures extending from the primary fractures,possibly dendritically, may be formed during a fracturing operation.These fractures may be vertical, horizontal, or a combination ofdirections forming a tortuous path.

Proppant particulates are often included in a fracturing fluid in orderto keep the fractures open after the hydraulic pressure has beenreleased following a hydraulic fracturing operation. Upon reaching thefractures, the proppant particulates settle therein to form a proppantpack to prevent the fractures from closing once the hydraulic pressurehas been released.

There are oftentimes difficulties encountered during hydraulicfracturing operations, particularly associated with deposition ofproppant particulates in fractures that have been created or extendedunder hydraulic pressure. Because proppant particulates are often densematerials, effective transport of the proppant particulates may bedifficult due to settling, making it challenging to distribute theproppant particulates into more remote reaches of a network offractures. In addition, fine-grained particles (referred to as “fines”)produced from crushing of proppant particulates within the fractures canalso lessen fluid conductivity, which may decrease production ratesand/or necessitate wellbore cleanout operations.

Lower density particles like coke have been used in fracturingoperations, for example, as described in U.S. Pat. No. 3,664,420. Insaid patent, the coke is used as a far-field diverter and not aproppant. Far-field diverters pack into the tip or end of the primaryand secondary fractures to form a very low-permeability zone. In thepatent, after the far-field diverters are pumped into the fracture tips,proppant particles of higher density and larger size (e.g., metallicshot) are packed into the majority of the fractures to formhigh-permeability zones.

SUMMARY OF THE INVENTION

The present disclosure generally relates to fracturing and, morespecifically, to proppant particulates for fracturing that are formedfrom flexicoke, and methods related thereto.

A nonlimiting example fracturing fluid of the present disclosurecomprises: a carrier fluid; and proppant particulates composed offlexicoke material.

A nonlimiting example method of the present disclosure comprises:introducing a fracturing fluid into a subterranean formation, thefracturing fluid comprising a carrier fluid and proppant particulatescomposed of flexicoke material.

The proppant particulates may have one or more of: a bulk density ofless than about 1.0 g/cm³; an apparent density in the range of about 1.0g/cm³ to about 2.0 g/cm³; a carbon content of about 85 wt % to about 99wt %; a weight ratio of carbon to hydrogen of about 80:1 to about 98:1;an impurities content of about 1 wt % to about 15 wt %; a sulfur contentof about 0 wt % to about 5 wt %; a nitrogen content of about 0 wt % toabout 3 wt %; a combined vanadium and nickel content of about 3000 ppmto about 45,000 ppm; a crush strength of about 3000 psi to about 12,000psi; a Krumbein roundness value of ≥0.6; a Krumbein sphericity of ≥0.6;and an average particle size distribution in the range of about 150 μmto about 300 μm.

BRIEF DESCRIPTION OF DRAWINGS

The following drawings are included to illustrate certain aspects of theembodiments, and should not be viewed as exclusive embodiments. Thesubject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to those skilled in the art and having the benefit of thisdisclosure.

FIG. 1 shows a particle size distribution chart of samples of flexicokeproppant particulates for use in one or more aspects of the presentdisclosure.

FIG. 2 shows a mercury porosimetry chart of a sample of flexicokeproppant particulates for use in one or more aspects of the presentdisclosure.

FIG. 3 shows a nitrogen adsorption chart of a sample of flexicokeproppant particulates for use in one or more aspects of the presentdisclosure.

FIG. 4A shows a chart of the results of long-term conductivity testingof samples of flexicoke proppant particulates for use in one or moreaspects of the present disclosure.

FIG. 4B shows a sieve size chart of the size of the tested flexicokeproppant particulate samples of FIG. 4A both before and after conductingthe long-term conductivity testing.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure generally relates to fracturing and, morespecifically, to proppant particulates for fracturing that are formedfrom flexicoke, and methods related thereto.

As discussed above, proppant particulates can be used effectively duringfracturing operations, but there may be issues associated with theiruse. First, the high densities of typical proppant particulates mayhinder their transport, possibly leading to inadequate proppantparticulate disposition within one or a plurality of fractures. Second,some proppant particulates are prone to fines formation due to low crushstrength values, which may lead to decreased fracture conductivity dueto fines accumulation within a wellbore.

The present disclosure alleviates the foregoing difficulties andprovides related advantages as well. In particular, the presentdisclosure provides proppant particulates formed from flexicoke that mayexhibit low densities and high crush strengths, thereby addressing twosignificant shortcomings of traditional proppant particulates, generallyformed from sand particles.

Typically, flexicoke is used as a fuel source in various manufacturingprocesses for heat. However, flexicoke is a low BTU source. By usingflexicoke as proppant and higher BTU fuel sources, the CO₂ emissions arereduced. In effect, using flexicoke as proppant is a form ofsequestering carbon that would otherwise contribute to CO₂ emissions.

Moreover, the costs associated with hydraulic fracturing may also bereduced at least because large volumes of flexicoke are readilyavailable from already existent petroleum refinery process streams andare typically cost-competitive to sand; and their low density maydecrease or eliminate the need to use gelled fracturing fluids (and thecosts associated with gelation), thereby potentially reducing requiredpumping pressures, water consumption, and wellbore cleanout operations.

Flexicoke is produced from a modified variation of fluid coking, termedFLEXICOKING™ (trademark of ExxonMobil Research and Engineering Company(“ExxonMobil”)). FLEXICOKING™ is based on fluidized bed technologydeveloped by ExxonMobil, and is a carbon rejection process that is usedfor upgrading heavy hydrocarbon feeds (referred to as “residua”). Unlikefluid coking, with utilizes a reactor and a burner, the FLEXICOKING™process uses a reactor, a heater, and a gasifier. The FLEXICOKING™process is described in greater detail below.

Illustrative aspects of the present disclosure include fracturing fluidscomprising proppant particulates composed of flexicoke, derived from aFLEXICOKING™ process and comprising at least partially gasified fluidcoke. The flexicoke proppant particulates are suitable for propping oneor more fractures induced during a hydraulic fracturing operation withina horizontal, vertical, or tortuous wellbore, includinghydrocarbon-bearing production wellbores and water-bearing productionwellbores.

Definitions and Test Methods

As used herein, the term “proppant particulate” refers to a solidmaterial capable of maintaining open an induced fracture during andfollowing a hydraulic fracturing treatment. The term “proppant pack”refers to a collection of proppant particulates.

As used herein, the term “flexicoke” refers to the solid concentratedcarbon material produced from FLEXICOKING™. The term “FLEXICOKING™”refers to a thermal cracking process utilizing fluidized solids andgasification for the conversion of heavy, low-grade hydrocarbon feedsinto lighter hydrocarbon products (e.g., upgraded, more valuablehydrocarbons). The term “flexicoke proppant particulates” refers toproppant particulates composed of flexicoke (i.e., partially gasifiedfluid coke).

As used herein, the term “apparent density,” with reference to thedensity of proppant particulates, refers to the density of theindividual particulates themselves, which may be expressed in grams percubic centimeter (g/cm³). The apparent density values of the presentdisclosure are based on the American Petroleum Institute's RecommendedPractice 19C (hereinafter “API RP-19C”) standard entitled “Measurementof Properties of Proppants Used in Hydraulic Fracturing andGravel-packing Operations” (First Ed. May 2008, Reaffirmed June 2016).

As used herein, the term “bulk density,” with reference to the densityof proppant particulates, refers to the density of a proppant pack,which may be expressed in g/cm³. The bulk density values of the presentdisclosure are based on API RP-19C.

As used herein, D10, D50, and D90 are primarily used herein to describeparticle sizes. As used herein, the term “D10” refers to a diameter atwhich 10% of the sample (on a volume basis unless otherwise specified)is comprised of particles having a diameter less than said diametervalue. As used herein, the term “D50” refers to a diameter at which 50%of the sample (on a volume basis unless otherwise specified) iscomprised of particles having a diameter less than said diameter value.As used herein, the term “D90” refers to a diameter at which 90% of thesample (on a volume basis unless otherwise specified) is comprised ofparticles having a diameter less than said diameter value. Particle sizecan be determined by light scattering techniques or analysis of opticaldigital micrographs. Unless otherwise specified, light scatteringtechniques are used for analyzing particle size.

As used herein, the term “crush strength,” with reference to proppantparticulates, refers to the stress load proppant particulates canwithstand prior to crushing (e.g., breaking or cracking). The crushstrength values of the present disclosure are based on API RP-19C.

As used herein, the term “fracture conductivity” refers to thepermeability of a proppant pack to conduct fluid at various stress(pressure) levels. The fracture conductivity values of the presentdisclosure are based on the American Petroleum Institute's RecommendedPractice 19D (API RP-19D) standard entitled “Measuring the Long-TermConductivity of Proppants” (First Ed. May 2008, Reaffirmed May 2015).

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” with respect to theindicated value, and take into account experimental error and variationsthat would be expected by a person having ordinary skill in the art.

As used in the present disclosure and claims, the singular forms “a,”“an,” and “the” include plural forms unless the context clearly dictatesotherwise.

The term “and/or” as used in a phrase such as “A and/or B” herein isintended to include “A and B,” “A or B,” “A,” and “B.”

Proppants, Methods, and Systems

Hydraulic fracturing operations require effective proppant particulatesto maintain the permeability and conductivity of a production well, suchas for effective hydrocarbon recovery. Effective proppant particulatesare typically associated with a variety of particular characteristics orproperties, including efficient proppant particulate transport within acarrier fluid, sufficient crush strength to maintain fractures proppedupon the removal of hydraulic pressure, and efficient conductivity oncethe wellbore is brought on production.

The rate of settling of a proppant particulate within a fracturing fluidat least in part determines its transport capacity within one or morefractures created during a hydraulic fracturing operation. The rate ofsettling of a proppant particulate may be determined using Equation 1:

$\begin{matrix}{{v = {\frac{\rho_{p} - \rho_{f}}{18\eta}g\sigma^{2}}},} & {{Equation}\mspace{14mu} 1}\end{matrix}$where v is the proppant particle; ρ_(p)−ρ_(f) is proportional to thedensity difference between the proppant particle and the carrier fluid;η is the viscosity of the carrier fluid; g is the gravitationalconstant; and σ² is proportional to the square of the proppantparticulate size. As will be appreciated, proppant particulates havinglower apparent densities and/or smaller average particle sizes settle ata slower rate within an identical carrier fluid (thus having bettertransport) compared to higher apparent density and/or larger averageparticle sized proppant particulates.

A proppant particulate's crush strength is a measure of its ability towithstand stresses within a fracture, as they must resist sustainedloads within a fractured subterranean formation during the lifetime of awellbore to maintain its conductivity. Proppant particulates that arenot able to withstand the imposed stresses of a fracture will crush overtime, resulting in the formation of fines that may be transported intothe wellbore with produced fluids and accumulate in sufficientquantities to decrease production rates and/or necessitate costlywellbore cleanout operations. Accordingly, proppant particulates withhigher crush strengths are favorable. Such higher strength proppantparticulates would additionally serve to promote fracture conductivity,particularly under increasing stresses. According to API RP-19Cstandards, adequate proppant particulates should have a crush strengthin which less than 10% of fines are produced under a stress of 5,000psi.

Proppant particulate efficacy is further related to fractureconductivity, characterized by the fluid flow rate in a propped fractureunder gradient pressure, the fracture being propped by a proppant pack.Fracture conductivity, C_(f), is the product of the proppant packpermeability, k, and its thickness, h, and may be determined usingEquations 2 and 3:

$\begin{matrix}{{C_{f} = {kh}},} & {{Equation}\mspace{14mu} 2} \\{{k = {\frac{1}{C}\frac{\phi^{3}}{\left( {1 - \phi} \right)^{2}}\sigma_{eff}^{2}\Phi_{s}^{2}}},} & {{Equation}\mspace{14mu} 3}\end{matrix}$where C is a constant; ϕ is the proppant pack void fraction; σ is theaverage particle size diameter of the proppant particulates; and Φ is ashape factor related to the asphericity of the proppant particulates. Intension with settling rate and transport, fracture conductivity favorsproppant particulates having larger average particle size diameters, aswell as thick proppant packs and narrow particle size distribution.

The flexicoke proppant particulates having the characteristics describedherein exhibit the aforementioned properties, as well as others, whichmake them not only a viable alternative for traditional sand proppantparticulates, but further a surprising substitute with enhancedfunctionality. The FLEXICOKING™ process is very different from fluid ordelayed coking processes and as such the mechanical properties of thecarbon produced cannot be anticipated.

Briefly, the FLEXICOKING™ process in which the flexicoke for forming theflexicoke proppant particulates described herein, integrates a crackingreactor, a heater, and a gasifier into a common fluidized-solids (coke)circulating system. A feed stream (of residua) is fed into a fluidizedbed, along with a stream of hot recirculating material to the reactor.From the reactor, a stream containing coke is circulated to the heatervessel, where it is heated. The hot coke stream is sent from the heaterto the gasifier, where it reacts with air and steam. The gasifierproduct gas, referred to as coke gas, containing entrained cokeparticles, is returned to the heater and cooled by cold coke from thereactor to provide a portion of the reactor heat requirement, which istypically about 496° C. to about 538° C. A return stream of coke sentfrom the gasifier to the heater provides the remainder of the heatrequirement. The coke meeting the heat requirement is then circulated tothe reactor and the feed stream is thermally cracked to produce lighthydrocarbon liquids that are removed from the reactor and recoveredusing conventional fractionating equipment. Fluid coke is formed fromthe thermal cracking process and settles (deposits) onto the “seed”fluidized bed coke already present in the reactor—the resultant at leastpartially gasified coke is flexicoke. In some instances, the coke fromthe thermal cracking process deposits in a pattern that appearsring-like atop the surface of the seed coke. Flexicoke is continuouslywithdrawn from the system during normal FLEXICOKING™ processing (e.g.,from the reactor or after it is streamed to the heater via anelutriator) to ensure that the system maintains particles of coke in afluidizable particle size range. Accordingly, flexicoke is a readilyavailable byproduct of the FLEXICOKING™ process.

Flexicoke produced from the FLEXICOKING™ process is quite different incomposition than fluid cokes produced by the fluid coking process, aswell as cokes produced using delayed coking. The gasification process ofFLEXICOKING™ results in substantial concentration of metals in theflexicoke product and additionally allows for operationaldesulfurization of sulfur from the flexicoke. The gasification can beminimized or maximized to influence the sulfur content(minimization=lower sulfur content). Accordingly, unlike cokes formed inother processes, flexicoke has a comparatively high metal content and acomparatively lower sulfur content that can be manipulated. Notably,high metal content particles have not been considered adequatehistorically for use as proppant particulates, because such particleswere considered to likely have low crush strengths incapable ofwithstanding formation pressures within fractures. However, as shownbelow, flexicoke exhibits the properties, including crush strength, foruse as a proppant particulate.

The flexicoke proppant particulates described herein may have a carboncontent of about 85 wt % to about 99 wt %, or about 90 wt % to about 96wt %.

The flexicoke proppant particulates described herein may have a weightratio of carbon to hydrogen of about 80:1 to about 98:1, or about 85:1to about 95:1.

The flexicoke proppant particulates described herein may have animpurities content (weight percent of all components other than carbonand hydrogen) of about 1 wt % to about 15 wt %, or about 3 wt % to about10 wt %.

Flexicoke has a higher metal content than other cokes. The flexicokeproppant particulates described herein may have a combined vanadium andnickel content of about 3000 ppm to about 45,000 ppm, or about 3000 ppmto about 15,000 ppm, or about 5000 ppm to about 30,000 ppm, or about30,000 ppm to about 45,000 ppm.

The flexicoke proppant particulates described herein may have a sulfurcontent of 0 wt % to about 5 wt %, or about 0.5 wt % to about 4 wt %.

The flexicoke proppant particulates described herein may have a nitrogencontent of 0 wt % to about 3 wt %, or about 0.1 wt % to about 2 wt %.

The apparent density of the flexicoke proppant particulates of thepresent disclosure may be in the range of about 1.0 grams per cubiccentimeter (g/cm³) to about 2.0 g/cm³, or about 1.4 g/cm³ to about 2.0g/cm³, or about 1.4 g/cm³ to about 1.6 g/cm³. Traditional sand proppantparticulates generally have apparent densities greater than about 2.5g/cm³. Thus, the flexicoke proppant particulates described herein havesubstantially lesser apparent densities compared to traditional sandproppant particulates, which is indicative of their comparably moreeffective transport and lower settling rates within a fracture formed aspart of a hydraulic fracturing operation.

The bulk density of the flexicoke proppant particulates of the presentdisclosure may be less than about 1.0 g/cm³, including in the range ofabout 0.5 g/cm³ to about 1.0 g/cm³, or about 0.7 g/cm³ to about 0.9g/cm³, or less than about 0.8 g/cm³. As described above, bulk densitymay be indicative of the crush strength of a proppant material, favoringhigher bulk densities to obtain greater crush strength. Surprisingly,the bulk densities of the flexicoke proppant particulates describedherein are lower compared to traditional sand proppant particulates,which may be greater than about 1.3 g/cm³, and yet the flexicokeproppant particulates maintain comparable or higher crush strengths atcomparable particle sizes, as described below. Without being limited bytheory, low density materials such as polymers generally have acompressive strength that is much less than sand, silica, and otherceramic materials, which have densities in a range of 2 g/cm³ to 3g/cm³. Many low-density materials have good elastic properties intension but are not as good in compression and often exhibit bucklingand creep in compression testing. Further, low-density carbonparticulate materials produced by high-temperature carbonizing materialssuch as coconut shells, bamboo, cotton, flax, and wood have veryinferior mechanical properties. Engineered carbon fibers can break thisparadigm, where many engineered carbon fibers have excellent propertiesin compression. Coke particles, at first glance, would generally beexpected to have properties similar to low-density carbon particulatematerials. However, it has been surprisingly observed that flexicokeparticles have sufficiently high crush strength to be suitable for useas proppant.

Typical proppant particulates are comprised of sand having particlediameters ranging from about 100 micrometers (μm) to about 1000 μm. Theflexicoke proppant particulates described herein are comparable inparticle diameter size having a D50 of about 50 μm to about 500 μm, orabout 100 μm to about 400 μm, or about 150 μm to about 350 μm.

As shown below, the deformation of the flexicoke proppant particulatesof the present disclosure may be at least partially size dependent. Insome aspects, the crush strength of the flexicoke proppant particulatesdescribed herein may be in the range of about 3000 psi to about 12,000psi, or about 3000 psi to about 6000 psi, or about 5000 psi to about10,000 psi, or about 7500 psi to about 12,000 psi.

The Krumbein Chart provides an analytical tool to standardize visualassessment of the sphericity and roundness of particles, includingproppant particulates. Each of sphericity and roundness is visuallyassessed on a scale of 0 to 1, with higher values of sphericitycorresponding to a more spherical particle and higher values ofroundness corresponding to less angular contours on a particle'ssurface. According to API RP-19C standards, the shape of a proppantparticulate is considered adequate for use in hydraulic fracturingoperations if the Krumbein value for both sphericity and roundness is≥0.6. As shown in the examples below, the shape of all but one sample offlexicoke proppant particulates tested herein exhibit a Krumbein valuefor both sphericity and roundness that is ≥0.6, and thus are suitablefor use as proppant particulates.

The long-term conductivity of a proppant pack comprising the flexicokeproppant particulates of the present disclosure is comparable totraditional sand proppant particulates, particularly at comparableparticle sizes, as shown herein below. Moreover, it is believed, withoutbeing bound by theory, that flexicoke proppant particulates may exhibitgreater ductility compared to traditional sand proppant particulates,comparably decreasing their fines production under increasing stress.

The flexicoke proppant particulates described herein may be used as partof a fracturing fluid, comprising a flowable (e.g., liquid or gelled)carrier fluid and one or more optional additives. This fluid is usuallyformulated at the well site in a mixing process that is conducted whileit is being pumped in the hydraulic fracturing process. When the fluidis formulated at the well site, flexicoke coke particles can be added ina manner similar to the known methods for adding sand into thefracturing fluid. In some aspects, it may be preferred that flexicokematerial received from a FLEXICOKING™ process are first processed (e.g.,at the manufacturing facility) to remove any undesirably sized materialthat has adhered or otherwise conglomerated prior to use as proppantparticulates. Optionally the removal process can be skipped, conductedat another facility, or be done in the field. In other or additionalaspects, any fines may be preferably removed from the flexicoke proppantparticulates, such as by use of bag filters, whether in storage orduring transport. As such, a more uniform size distribution may beobtained. In addition to the flexicoke proppant particulates, it iswithin the scope of the present disclosure that the flexicoke proppantparticulates be included alone or in combination with one or more othertypes of proppant particulates. When flexicoke proppant particulates areincluded in combination with another type of proppant particle, thevarious particles can be mixed as a dry solid, mixed in a slurry, oradded separately into a fracturing fluid that is being formulated at thewell site.

The carrier fluid of the present disclosure may be an aqueous-basedfluid or a nonaqueous-based fluid. Aqueous-based fluids may include, forexample, fresh water, saltwater (including seawater), treated water(e.g., treated production water), other forms of aqueous fluid, and anycombination thereof. One aqueous based fluid class is often referred toas slickwater, and the corresponding fracturing operations are calledslickwater fracturing. Nonaqueous-based fluids may include, for example,oil-based fluids (e.g., hydrocarbon, olefin, mineral oil), alcohol-basedfluids (e.g., methanol), and any combination thereof.

In various aspects, the viscosity of the carrier fluid may be altered byfoaming or gelling. Foaming may be achieved using, for example, air orother gases (e.g., CO₂, N₂), alone or in combination. Gelling may beachieved using, for example, guar gum (e.g., hydroxypropyl guar),cellulose, or other gelling agents, which may or may not be crosslinkedusing one or more crosslinkers, such as polyvalent metal ions or borateanions, among other suitable crosslinkers.

In some instances, the carrier fluid used in hydraulic fracturing ofhorizontal wells is one or more of an aqueous-based fluid type,particularly in light of the large volumes of fluid typically requiredfor hydraulic fracturing (e.g., about 60,000 to about 1,000,000 gallonsper wellbore). The aqueous-based fluid may or may not be gelled. Gelled,either crosslinked or uncrosslinked, fluids may facilitate betterproppant particulate transport (reduced settling), as well as improvedphysical and chemical strength to withstand the temperature, pressure,and shear stresses encountered by the fracturing fluid during ahydraulic fracturing operation. In some instances, the fracturing fluidmay comprise an aqueous-based carrier fluid, which may or may not befoamed or gelled, and an acid (e.g., HCl) to further stimulate andenlarge pore areas of the matrix of fracture surfaces. It is to beappreciated that the low density of the flexicoke proppant particulatesdescribed herein may allow a reduction or elimination of the need tofoam or gel the carrier fluid.

In addition, certain fracturing fluids suitable for use in the presentdisclosure may contain one or more additives such as, for example,dilute aids, biocides, breakers, corrosion inhibitors, crosslinkers,friction reducers (e.g., polyacrylamides), gels, salts (e.g., KCl),oxygen scavengers, pH control additives, scale inhibitors, surfactants,weighting agents, inert solids, fluid loss control agents, emulsifiers,emulsion thinners, emulsion thickeners, viscosifying agents,particulates, lost circulation materials, foaming agents, gases,buffers, stabilizers, chelating agents, mutual solvents, oxidizers,reducers, clay stabilizing agents, and any combination thereof.

The present disclosure includes methods of hydraulic fracturing using afracturing fluid comprising flexicoke proppant particulates, alone or incombination with other proppant particulates, during a hydraulicfracturing operation. That is, the flexicoke proppant particulates formthe entirety of a proppant pack, or may form an integral part of aproppant pack. Other proppant particulate types that may be utilizedwith the flexicoke proppant particulates described herein include, butare not limited to, the traditional sand proppant particulates describedherein, as well as those made from bauxite, ceramic, glass, and anycombination thereof, and may or may not have surface modifications.Proppant particulates composed of other materials are also within thescope of the present disclosure, provided that any such selectedproppant particulates (including those composed of the aforementionedmaterials) are able to maintain their integrity upon removal ofhydraulic pressure within an induced fracture, such that about 80%,preferably about 90%, and more preferably about 95% or greater of theparticle mass of the other proppant particulates retains integrity whensubjected to 5000 psi of stress, a requirement also met by the flexicokeproppant particulates of the present disclosure. That is, both theflexicoke proppant particulates and any other proppant particulates usedin the methods described herein must maintain mechanical integrity uponfracture closure, as both types of particulates must intermingle orotherwise associate to form functional proppant packs for a successfulhydraulic fracturing operation.

The methods described herein include preparation of fracturing fluid,which is not considered to be particularly limited, because theflexicoke proppant particulates are capable of transportation in dryform or as part of a wet slurry from a manufacturing site (e.g., arefinery or synthetic fuel plant). Dry and wet forms may be transportedvia truck or rail, and wet forms may further be transported viapipelines. The transported dry or wet form of the flexicoke proppantparticulates may be added to a carrier fluid, including optionaladditives, at a production site, either directly into a wellbore or bypre-mixing in a hopper or other mixing equipment. In some aspects, forexample, when the entirety of the proppant particulates within thefracturing fluid at a given time are flexicoke proppant particulates,slugs of the dry or wet form may be added directly to the fracturingfluid (e.g., as it is introduced into the wellbore). These slugs of onlyflexicoke proppant particulates may be followed by subsequent slugs of,again, only flexicoke proppant particulates or of a mixture of flexicokeproppant particulates and other proppant particulates. In other aspects,such as when other proppant particulate types are combined with theflexicoke proppant particulates, a portion or all of the fracturingfluid may be pre-mixed at the production site or each proppant type maybe added directly to the fracturing fluid separately. Any other suitablemixing or adding of the flexicoke proppant particulates to produce adesired fracturing fluid composition may also be used, without departingfrom the scope of the present disclosure.

The methods of hydraulic fracturing suitable for use in one or moreaspects of the present disclosure involve pumping fracturing fluidcomprising flexicoke proppant particulates at a high pump rate into asubterranean formation to form at least a primary fracture, as well aspotentially one or more secondary fractures extending from the primaryfracture, one or more tertiary fractures extending from the secondaryfractures, and the like (all collectively referred to as a “fracture”).In a preferred embodiment, this process is conducted one stage at a timealong a horizontal well. The stage is hydraulically isolated from anyother stages which have been previously fractured. In one embodiment,the stage being fractured has clusters of perf holes (e.g., perforationsin the wellbore and/or subterranean formation) allowing flow ofhydraulic fracturing fluid through a metal tubular casing of thehorizontal well into the formation. Such metal tubular casings areinstalled as part of the completions when the well is drilled and serveto provide mechanical integrity for the horizontal wellbore. In someaspects, the pump rate for use during hydraulic fracturing may be atleast about 20 barrels per minute (bbl/min), preferably about 30bbl/min, and more preferably in excess of 50 bbl/min and less than 1000bbl/min at one or more time durations during the fracturing operation(e.g., the rate may be constant, steadily increased or pulsed). Thesehigh rates may, in some aspects, be utilized after about 10% of theentire volume of fracturing fluid to be pumped into the formation hasbeen injected. That is, at the early periods of a hydraulic fracturingoperation, the pump rate may be lower and as fracture(s) begin to form,the pump rate may be increased. Generally, the average pump rate of thefracturing fluid throughout the operation may be about 10 bbl/min,preferably about 15 bbl/min, and more preferably in excess of 25bbl/minute and less than 250 bbl/min. Typically, the pump rate during afracturing operation for more than 30% of the time required to completefracturing of a stage is in the range of about 20 bbl/min to about 150bbl/min, or about 40 bbl/min to about 120 bbl/min, or about 40 bbl/minto about 100 bbl/min.

In various aspects, the methods of hydraulic fracturing described hereinmay be performed wherein the concentration of the proppant particulates(including flexicoke proppant particulates and any other proppantparticulates) within the injected fracturing fluid is altered (i.e.,on-the-fly while the fracturing operation is being performed, such thathydraulic pressure is maintained within the formation and fracture(s)).For example, in some aspects, the initially injected fracturing fluidmay be injected at a low pump rate and may comprise 0 volume % (vol %)to about 1 vol % proppant particulates. As one or more fractures beginto form and grow, the pump rate is increased and the concentration ofproppant particulates may be increased in a stepwise fashion (with orwithout a stepwise increase in pump rate) with a maximum concentrationof proppant particulates reaching about 2.5 vol % to about 20 vol %,encompassing any value and subset therebetween. For example, the maximumconcentration of proppant particulates may reach at least 2.5 vol %,preferably about 8 vol %, and more preferably about 16 vol %. In someaspects, all of the proppant particulates are flexicoke proppantparticulates. In other aspects, at one or more time periods during thehydraulic fracturing operation, at least about 2 vol % to about 100 vol% of any proppant particulates suspended within the fracturing fluid areflexicoke proppant particulates, such as at least about 2 vol %,preferably about 15 vol %, more preferably about 25 vol %, and even morepreferably 100 vol %.

It should be noted that some or all of the flexicoke proppant particlesmay be coated. Coatings are often used on sand particles used inhydraulic fracturing to either improve their flowability or to mitigatetheir flow back during production. Such types of coatings are within thescope of this invention. It is possible to introduce coated flexicokeproppant particles at any stage of the hydraulic fracturing process withthe resulting flexicoke composition being either a mixture of coated anduncoated flexicoke or entirely coated flexicoke.

In one or more aspects, the flexicoke proppant particulates may beintroduced after about ⅛ to about ¾ of the total volume of fracturingfluid has been injected within a formation. Because of the low densityof the flexicoke proppant particulates, it may be beneficial tointroduce the flexicoke proppant particulates during later time periodsof fracturing after which the fracture(s) have already grownsubstantially, such that the flexicoke proppant particulates can travelwithin the fracturing fluid to remote locations of the formedfracture(s). Denser proppant particulates would not be able to reachthese remote locations due to settling effects, for example.

The hydraulic fracturing methods described herein may be performed indrilled horizontal, vertical, or tortuous wellbores,hydrocarbon-producing (e.g., oil and/or gas) wellbores andwater-producing wellbores. These wellbores may be in varioussubterranean formation types including, but not limited to, shaleformations, oil sands, gas sands, and the like.

The wellbores are typically completed using a metal (e.g., steel)tubular or casing that is cemented into the subterranean formation. Tocontact the formation, a plurality of perforations are created throughthe tubular and cement along a section to be treated, usually referredto as a plug and perforated (“plug and perf”) cased-hole completion.Alternative completion techniques may be used without departing from thescope of the present disclosure, but in each technique, a finite lengthof the wellbore is exposed for hydraulic fracturing and injection offracturing fluid. This finite section is referred to herein as a“stage.” In plug and perf completions, the stage length may be based adistance over which the tubular and cement has been perforated, and maybe in the range of about 10 feet (ft) to about 2000 ft, for example, andmore generally in the range of about 100 ft to about 300 ft. The stageis isolated (e.g., sliding sleeve, ball) such that pressurizedfracturing fluid from the surface can flow through the perforations andinto the formation to generate one or more fractures in only the stagearea. Clusters of perforations may be used to facilitate initiation ofmultiple fractures. For example, clusters of perforations may be made insections of the stage that are about 1 ft to about 3 ft in length, andspaced apart by about 2 ft to about 30 ft.

For each linear foot of the stage, at least about 6 barrels (about 24cubic feet (ft³)), preferably about 24 barrels (about 135 ft³), and morepreferably at least 60 barrels (about 335 ft³) and less than 6000barrels (about 33,500 ft³) of fracturing fluid may be injected to growthe one or more fractures. In certain aspects, for each linear foot ofthe stage, at least about 1.6 ft³, preferably about 6.4 ft³, and morepreferably at least 16 ft³ and less than 1600 ft³ of proppantparticulates may be injected to prop the fractures. In some aspects, toprevent bridging of the proppant particulates during injection into thefractures, the ratio of the volume of the proppant particulates to theliquid portion of the fracturing fluid, primarily the carrier fluid, isgreater than 0 and less than about 0.25 and preferably less than about0.15. If the volume ratio becomes too large a phenomena known as“sanding out” will occur.

Certain commercial operations, such as commercial shale fracturingoperations, may be particularly suitable for hydraulic fracturing usingthe flexicoke proppant particulates and methods described herein, as themass of proppant particulates required per stage in such operations canbe quite large and substantial economic benefit may be derived using theflexicoke proppant particulates. The cost of flexicoke particles can beless than the cost of sand, which provides a significant economicbenefit. Indeed, in some instances, a stage in a shale formation may bedesigned to require at least about 30,000, preferably about 100,000, andmore preferably about 250,000 pounds (mass) of proppant particulates. Insuch cases, economic and performance benefit may be optimized when atleast about 5%, preferably more than about 25%, and up to 100% of theproppant particulate mass comprises flexicoke proppant particulates.

Multiple stages of the wellbore are isolated and hydraulic fracturingperformed at each stage. The flexicoke proppant particulates of thepresent disclosure may be used in any one, more, or all more stages,including at least 2 stages, preferably at least 10 stages, and morepreferably at least 20 stages.

Example Embodiments

A first nonlimiting example embodiment of the present disclosure is afracturing fluid comprising: a carrier fluid; and proppant particulatescomposed of flexicoke material. The first nonlimiting example embodimentmay include one or more of: Element 1: wherein the proppant particulateshave a bulk density of less than about 1.0 g/cm³; Element 2: wherein theproppant particulates have an apparent density in the range of about 1.0g/cm³ to about 2.0 g/cm³; Element 3: wherein the flexicoke proppantparticulates have one or more of: (a) a carbon content of about 85 wt %to about 99 wt %, (b) a weight ratio of carbon to hydrogen of about 80:1to about 98:1, (c) an impurities content of about 1 wt % to about 15 wt%, (d) a sulfur content of about 0 wt % to about 5 wt %, (e) a nitrogencontent of about 0 wt % to about 3 wt %; and (f) a combined vanadium andnickel content of about 3000 ppm to about 45,000 ppm; Element 4: whereinthe proppant particulates have a crush strength of about 3000 psi toabout 12,000 psi; Element 5: wherein the proppant particulates have aKrumbein roundness value of ≥0.6; Element 6: wherein the proppantparticulates have a Krumbein sphericity of ≥0.6; Element 7: wherein theproppant particulates have an average particle size distribution in therange of about 150 μm to about 300 μm; Element 8: wherein the carrierfluid is an aqueous carrier fluid; and Element 9: the fracturing fluidfurther comprising second proppant particulates composed of a materialthat is not a flexicoke material. Examples of combinations include, butare not limited to, Element 1 in combination with one or more ofElements 2-9, Element 2 in combination with one or more of Elements 3-9,Element 3 in combination with one or more of Elements 4-9, Element 4 incombination with one or more of Elements 5-9, Element 5 in combinationwith one or more of Elements 6-9, Element 6 in combination with one ormore of Elements 7-9, Element 7 in combination with one or both ofElements 8-9, and Element 8 in combination with Element 9.

A second nonlimiting example embodiment of the present disclosure is amethod comprising: introducing a fracturing fluid into a subterraneanformation, the fracturing fluid comprising a carrier fluid and proppantparticulates composed of flexicoke material. The second nonlimitingexample embodiment may include one or more of: Element 1; Element 2;Element 3; Element 4; Element 5; Element 6; Element 7; Element 8;Element 9; Element 10: the method further comprising depositing at leasta portion of the proppant particulates within one or more fractures inthe subterranean formation; Element 11: the method further comprising:sequestering carbon in the subterranean formation in the form of theflexicoke material. Examples of combinations include, but are notlimited to, Element 1 in combination with one or more of Elements 2-11,Element 2 in combination with one or more of Elements 3-11, Element 3 incombination with one or more of Elements 4-11, Element 4 in combinationwith one or more of Elements 5-11, Element 5 in combination with one ormore of Elements 6-11, Element 6 in combination with one or more ofElements 7-11, Element 7 in combination with one or more of Elements8-11, Element 8 in combination with one or more of Elements 9-11,Element 9 in combination with one or both of Elements 10-11, and Element10 in combination with Element 11.

To facilitate a better understanding of the aspects of the presentdisclosure, the following examples of preferred or representativeaspects are given. In no way should the following examples be read tolimit, or to define, the scope of the disclosure.

EXAMPLES

In the following examples, properties of flexicoke proppant particulatesare compared to properties of traditional sand proppant particulates.The flexicoke proppant particulates were obtained from the ExxonMobilRefinery located in Baytown, Tex. The sand proppant particulatescomprised traditional 100 mesh Texas brown sands mined for use asproppant particulates in the Permian basin.

At the outset, the flexicoke proppant particulates for use in theexamples were characterized by size. The particle size distribution isshown in FIG. 1. As shown, about 82% of the flexicoke proppant particlesby weight were within a particle size range of about 74 μm to about 425μm. The average particle size (D50) of the flexicoke proppantparticulates was 197 μm; the D10 value was 119 μm; and the D90 value was319 μm. These sizes are comparable to the 100 mesh sand proppantparticles, which have an average particle size of 149 μm.

Example 1: Physical Property Characterization

Two (2) samples of flexicoke proppant particulates were sieved to obtaina size range between 147 μm and 250 μm and characterized using mercury(Hg) porosimetry and nitrogen (N₂) adsorption.

Hg Porosimetry. Standard mercury porosimetry was used to measure theinternal porosity of the sampled flexicoke proppant particulates. Theresults are shown in FIG. 2. As shown, the flexicoke proppantparticulates comprise minimum internal porosity in the 0.01 to 10.0 μmrange.

N₂ Adsorption. The nanopore volume and surface area of the flexicokeproppant particulates was measured using standard nitrogen adsorption.The results are shown in FIG. 3. As shown, the nanopore volume of theflexicoke proppant particulates is about 0.05 cm³/g and the surface areais about 60 m²/g.

Example 2: API Characterization

Three (3) experimental samples of the flexicoke proppant particulateswere sieved according to Table 1 below and compared to one (1) controlsample of the sand proppant particulates having an average particle sizeof 100 mesh (149 μm). The experimental flexicoke proppant particulatesamples are labeled EX1, EX2, and EX3 herein, and the control sandproppant particulates sample is labeled CL herein.

TABLE 1 Sample Sieve Size Range EX1 (−) 425 μm/(+) 230 μm EX2 (−) 230μm/(+) 140 μm EX3 (−) 140 μm/(+) 74 μm

Accordingly, the flexicoke proppant particulates in sample EX1 arelarger than the flexicoke proppant particulates in sample EX2, and theflexicoke proppant particulates in sample EX1 and EX2 are larger thanthe flexicoke proppant particulates in sample EX3.

Density. The EX1, EX2, EX3, and CL samples of Table 1 were tested usingAPI PR-19C for bulk density (ρ_(bulk)) and apparent density(ρ_(apparent)). The results are shown in Table 2 below.

TABLE 2 Sample ρ_(bulk) (g/cm³) ρ_(apparent) (g/cm³) EX1 0.74 1.46 EX20.77 1.47 EX3 0.79 1.53 CL 1.47 2.66

As shown in Table 2, the values for the bulk and apparent densities ofthe EX1, EX2, and EX3 flexicoke samples show vary little variation withrespect to sieved particle size. However, the EX1, EX3, and EX3 samplesexhibit substantially lower bulk and apparent densities compared to theCL sample—approximately half.

Crush Strength. The EX1, EX2, EX3, and CL samples of Table 1 were testedusing API PR-19C for crush strength. Each of the samples was initiallysieved using the sieve ranges shown in Table 3. The collected mediandiameter size (d_(med)) and average diameter size (<d>) are also shownin Table 3. The sieved samples were subject to increasing stress loadsand the stress level, in pounds per square inch (psi), at which 10% ofeach sample was crushed to a size below the smallest initial sieve rangeis shown in Table 3.

TABLE 3 Sample Sieve Size d_(med) (μm) <d> (μm) Crush (psi) EX1 40/70 288 292 6000 EX2 70/140 178 182 9000 EX3 70/140 106 108 2000 CL 50/140178 185 10000

As shown in Table 3, the EX2 sample exhibits a comparable crush strengthcompared to the CL sample, each having near identical proppantparticulate particle size. The EX1 sample exhibited a lower crushstrength, but would still meet the API RP-19C standard for use asproppant particulates, as described above. The EX3 sample exhibited amuch reduced crush strength compared to the other samples. Without beingbound by theory, it is believed that this result is due to the muchreduced particle size collected during the sieving process inpreparation for crush testing, such that the smaller sized particles fitthrough the mesh with even minimally applied stress. This suggests thatcrush strength for the flexicoke particles may be at least potentiallydependent on particle size, where a range of size is preferred in termsof crush strength compared to smaller or larger particles sizes outsideof side range.

Shape. The shape of the EX1, EX2, EX3, and CL samples of Table 1 wereexamined using the Krumbein Scale. As provided above, the shape of aproppant particulate is considered sufficient if the Krumbein value forboth sphericity and roundness is ≥0.6. The visual analysis for the EX1,EX2, EX3, and CL samples are shown in Table 4.

TABLE 4 Sample Sphericity Roundness EX1 0.6 0.5 EX2 0.6 0.6 EX3 0.6 0.7CL 0.6 0.7

Table 4 demonstrates that the EX2 and EX3 sphericity and roundnessvalues are compliant with the criterion Krumbein value of ≥0.6 and are,accordingly, sufficient for proppant particulate usage in terms ofshape. The sphericity of EX1 is 0.6. However, EX3 exhibited marginalroundness at 0.5.

Long-term Conductivity. The EX2, EX3, and CL samples of Table 1 weretested using API PR-19D for long-term conductivity. The results areshown in FIG. 4A and demonstrate that EX2 and CL exhibit comparablelong-term conductivity. As shown above, EX3 having relatively smallerparticles exhibited comparatively reduced long-term conductivity,indicating that smaller particles of flexicoke may be less preferable tocomparably larger particles of flexicoke as proppant particulates.

Prior to, and after, the long-term conductivity testing, the particlesize distribution of the EX2 and CL samples were evaluated forcomparison. The results are shown in FIG. 4B. Both of the EX2 and CLsamples experienced a shift in particle sieve size distribution towardsmaller mesh sizes after testing (applying closure pressure), but alarger fraction of the CL sample were finer in size (labeled “pan”)compared to the EX2 sample at the end of testing. Without being bound bytheory, it is believed that this result is associated with an increasedductility of the flexicoke material compared to traditional sand. Thatis, proppant pack permeability loss may be more influenced bydeformation and consolidation of proppant particulates and because sandis more brittle compared to flexicoke, it will maintain its shape andpermeability at certain stress levels, but begins to fail as stresslevels increase.

Accordingly, the flexicoke proppant particulates of the presentdisclosure are suitable for use in hydraulic fracturing operations,including in unconventional formation types.

As is apparent from the foregoing general description and the specificembodiments, while forms of the disclosure have been illustrated anddescribed, various modifications can be made without departing from thespirit and scope of the disclosure. Accordingly, it is not intended thatthe disclosure be limited thereby. For example, the compositionsdescribed herein may be free of any component, or composition notexpressly recited or disclosed herein. Any method may lack any step notrecited or disclosed herein. Likewise, the term “comprising” isconsidered synonymous with the term “including.” Whenever a method,composition, element or group of elements is preceded with thetransitional phrase “comprising,” it is understood that we alsocontemplate the same composition or group of elements with transitionalphrases “consisting essentially of,” “consisting of,” “selected from thegroup of consisting of,” or “is” preceding the recitation of thecomposition, element, or elements and vice versa.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the present specification and associated claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired propertiessought to be obtained by the embodiments of the present disclosure. Atthe very least, and not as an attempt to limit the application of thedoctrine of equivalents to the scope of the claim, each numericalparameter should at least be construed in light of the number ofreported significant digits and by applying ordinary roundingtechniques.

Whenever a numerical range with a lower limit and an upper limit isdisclosed, any number and any included range falling within the range isspecifically disclosed. In particular, every range of values (of theform, “from about a to about b,” or, equivalently, “from approximately ato b,” or, equivalently, “from approximately a-b”) disclosed herein isto be understood to set forth every number and range encompassed withinthe broader range of values. Also, the terms in the claims have theirplain, ordinary meaning unless otherwise explicitly and clearly definedby the patentee. Moreover, the indefinite articles “a” or “an,” as usedin the claims, are defined herein to mean one or more than one of theelement that it introduces.

One or more illustrative embodiments are presented herein. Not allfeatures of a physical implementation are described or shown in thisapplication for the sake of clarity. It is understood that in thedevelopment of a physical embodiment of the present disclosure, numerousimplementation-specific decisions must be made to achieve thedeveloper's goals, such as compliance with system-related,business-related, government-related and other constraints, which varyby implementation and from time to time. While a developer's effortsmight be time-consuming, such efforts would be, nevertheless, a routineundertaking for one of ordinary skill in the art and having benefit ofthis disclosure.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent disclosure may be modified and practiced in different butequivalent manners apparent to one having ordinary skill in the art andhaving the benefit of the teachings herein. Furthermore, no limitationsare intended to the details of construction or design herein shown,other than as described in the claims below. It is therefore evidentthat the particular illustrative embodiments disclosed above may bealtered, combined, or modified and all such variations are consideredwithin the scope and spirit of the present disclosure. The embodimentsillustratively disclosed herein suitably may be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein.

What is claimed is:
 1. A fracturing fluid comprising: a carrier fluid;and proppant particulates having an average particle size distributionof about 150 μm to about 300 μm and composed of flexicoke material thatis at least partially gasified coke.
 2. The fracturing fluid of claim 1,wherein the proppant particulates have a bulk density of less than about1.0 g/cm³.
 3. The fracturing fluid of claim 1, wherein the proppantparticulates have an apparent density in the range of about 1.0 g/cm³ toabout 2.0 g/cm³.
 4. The fracturing fluid of claim 1, wherein theflexicoke proppant particulates have one or more of: (a) a carboncontent of about 85 wt % to about 99 wt %, (b) a weight ratio of carbonto hydrogen of about 80:1 to about 98:1, (c) an impurities content ofabout 1 wt % to about 15 wt %, (d) a sulfur content of about 0 wt % toabout 5 wt %, (e) a nitrogen content of about 0 wt % to about 3 wt %; or(f) a combined vanadium and nickel content of about 3000 ppm to about45,000 ppm.
 5. The fracturing fluid of claim 1, wherein the proppantparticulates have a crush strength of about 3000 psi to about 12,000psi.
 6. The fracturing fluid of claim 1, wherein the proppantparticulates have a Krumbein roundness value of ≥0.6.
 7. The fracturingfluid of claim 1, wherein the proppant particulates have a Krumbeinsphericity of ≥0.6.
 8. The fracturing fluid of claim 1, wherein thecarrier fluid is an aqueous carrier fluid.
 9. A fracturing fluidcomprising: a carrier fluid; first proppant particulates composed offlexicoke material that is at least partially gasified coke; and secondproppant particulates composed of a material that is not a flexicokematerial.
 10. A method comprising: introducing a fracturing fluid into asubterranean formation, the fracturing fluid comprising a carrier fluidand proppant particulates having an average particle size distributionof about 150 μm to about 300 μm and composed of flexicoke material thatis at least partially gasified coke.
 11. The method of claim 10, furthercomprising: depositing at least a portion of the proppant particulateswithin one or more fractures in the subterranean formation.
 12. Themethod of claim 10, wherein the proppant particulates have a bulkdensity of less than about 1.0 g/cm³.
 13. The method of claim 10,wherein the proppant particulates have an apparent density in the rangeof about 1.0 g/cm³ to about 2.0 g/cm³.
 14. The method of claim 10,wherein the flexicoke proppant particulates have one or more of: (a) acarbon content of about 85 wt % to about 99 wt %, (b) a weight ratio ofcarbon to hydrogen of about 80:1 to about 98:1, (c) an impuritiescontent of about 1 wt % to about 15 wt %, (d) a sulfur content of about0 wt % to about 5 wt %, (e) a nitrogen content of about 0 wt % to about3 wt %; or (f) a combined vanadium and nickel content of about 3000 ppmto about 45,000 ppm.
 15. The method of claim 10, wherein the proppantparticulates have a crush strength of about 3000 psi to about 12,000psi.
 16. The method of claim 10, wherein the proppant particulates havea Krumbein roundness value of ≥0.6.
 17. The method of claim 10, whereinthe proppant particulates have a Krumbein sphericity of ≥0.6.
 18. Themethod of claim 10, wherein the carrier fluid is an aqueous carrierfluid.
 19. The method of claim 10, wherein the fracturing fluid furthercomprises second proppant particulates composed of a material that isnot a flexicoke material.
 20. The method of claim 10, furthercomprising: sequestering carbon in the subterranean formation in theform of the flexicoke material.